Smiling Alters Emotional Perceptions

Summary: Researchers discovered that a brief, electrically induced smile can make neutral faces seem happier, a revelation that holds promise for understanding emotional perception and potentially treating affective disorders. The study utilized facial electrical stimulation, a technique inspired by Charles Darwin’s work, to produce quick, involuntary smiles in participants.

This novel approach demonstrated that even a fleeting smile could significantly alter emotional perception, marking the first evidence of its kind. With implications for theoretical debates and clinical applications, this research could pave the way for new treatments for conditions like depression, Parkinson’s, and autism by enhancing facial emotion recognition.

Key Facts:

  1. Innovative Experimentation: Utilizing electrical stimulation, the study is the first to show that activating smile muscles makes neutral faces appear more joyful.
  2. Historical Inspiration: The technique modernizes methods developed by Duchenne de Boulogne and featured by Charles Darwin, applying controlled electrical currents to induce smiles with precision.
  3. Potential Clinical Applications: The findings open new avenues for exploring treatments for mood disorders and conditions affecting emotional expression, like Parkinson’s and autism, through improved understanding of facial feedback in emotion perception.

Source: University of Essex

Smiling for just a split second makes people more likely to see happiness in expressionless faces, new University of Essex research has revealed. 

The study led by Dr Sebastian Korb, from the Department of Psychology, shows that even a brief weak grin makes faces appear more joyful. 

The pioneering experiment used electrical stimulation to spark smiles and was inspired by photographs made famous by Charles Darwin. 

This shows a woman smiling.
It emerged that producing a weak smile for 500 milliseconds was enough to induce the perception of happiness. Credit: Neuroscience News

A painless current manipulated muscles momentarily into action – creating a short uncontrollable smile. 

This is the first time facial electrical stimulation has been shown to affect emotional perception. 

Dr Korb hopes the research can explore potential treatments for depression or disorders that affect expression, like Parkinson’s and autism.  

He said: “The finding that a controlled, brief and weak activation of facial muscles can literally create the illusion of happiness in an otherwise neutral or even slightly sad looking face, is ground-breaking. 

“It is relevant for theoretical debates about the role of facial feedback in emotion perception and has potential for future clinical applications.” 

Dr Korb used a modernised version of a technique first developed in the 19th century by the French physician Duchenne de Boulogne. 

Darwin published drawings of Duchenne’s work in The Expression of the Emotions in Man and Animals – his third major work on evolution. 

However, the voltage was dialled down for the new experiments to ensure the safety of participants and better control the smiles. 

By using computers, the team were able to control the onset of smiles with millisecond precision. 

In total 47 people took part in the Essex study which was published in Social Cognitive and Affective Neuroscience. 

They were shown digital avatars and asked to assess whether they looked happy or sad. In half the trials, smiling muscles were activated at the onset of the face. 

It emerged that producing a weak smile for 500 milliseconds was enough to induce the perception of happiness. 

Dr Korb says the results help us understand facial feedback and he hopes to expand the study. 

He said: “We are currently conducting more al research to further explore the phenomenon in healthy participants.  

“In the future, however, we hope to apply this technique to explore facial emotion recognition, for people with conditions like Parkinson’s, who are known to have reduced spontaneous facial mimicry and impaired facial emotion recognition.  

“Moreover, we have published guidelines to allow other researchers to safely start using electrical facial muscle stimulation.” 

About this emotional processing research news

Author: Ben Hall
Source: University of Essex
Contact: Ben Hall – University of Essex
Image: The image is credited to Neuroscience News

Original Research: Closed access.
Zygomaticus activation through facial neuromuscular electrical stimulation (fNMES) induces happiness perception in ambiguous facial expressions and affects neural correlates of face processing” by Sebastian Korb et al. Social Cognitive and Affective Neuroscience


Zygomaticus activation through facial neuromuscular electrical stimulation (fNMES) induces happiness perception in ambiguous facial expressions and affects neural correlates of face processing

The role of facial feedback in facial emotion recognition remains controversial, partly due to limitations of the existing methods to manipulate the activation of facial muscles, such as voluntary posing of facial expressions or holding a pen in the mouth. These procedures are indeed limited in their control over which muscles are (de)activated when and to what degree.

To overcome these limitations and investigate in a more controlled way if facial emotion recognition is modulated by one’s facial muscle activity, we used computer-controlled facial neuromuscular electrical stimulation (fNMES). In a pre-registered EEG experiment, ambiguous facial expressions were categorised as happy or sad by 47 participants.

In half of the trials, weak smiling was induced through fNMES delivered to the bilateral Zygomaticus Major muscle for 500 ms. The likelihood of categorising ambiguous facial expressions as happy was significantly increased with fNMES, as shown with frequentist and Bayesian linear mixed models. Further, fNMES resulted in a reduction of P1, N170 and LPP amplitudes.

These findings suggest that fNMES-induced facial feedback can bias facial emotion recognition and modulate the neural correlates of face processing. We conclude that fNMES has potential as a tool for studying the effects of facial feedback.

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